loopbacking on a port - How to

Hi in this video i'll show you how to make a loopback cable using a fibre LC duplex cable.

The aim of performing a loopback on a cable or port is to test if the port is Up physically. Before you start troubleshooting (TS) it’s a good idea to check your links config (admin state up or down).

Ports are TX and RX (Transmit and Receive), Ports have a receiving and sending attribute built into them. Our test will as follow:
Side A sends traffic to Side B.
Side B receives the traffic and sends it back to A.
If this scenario works our port should come up (green LED or another sort of indicator will light up). Led colours explained end of video.

If our port goes Up this suggest that the port in the Host and the transceiver is good.
If this fails, test your loopback on a known working port. If this still fails, your transceiver or the port itself is faulty.

[JKRowl]

Thank you for this video. But I’m confused about a few things here;

1- Were you testing the SFP port which is used for stacking switches?
2- At 01:27 what was this extenal port that you added, and how did light up without connecting end to end?
3- The loopback cable, can it be used to test all ports on a switch?

Thank you and I appologize if my questions were a lot.